I think you're confusing your terms. DLNA is all about streaming a media file from one device to another. The protocol describes how one device communicates with the other for streaming purposes.
Transcoding changes the media file to a format your renderer (tv, ps3, etc) can play. It happens on the server (PC)
before using DLNA to stream it to your ps3. Serviio can transcode media on the fly using a set of matching rules in the profile, and then uses DLNA to stream it to your ps3. It all appears to happen at the same time, but it's really two distinct processes.
The ps3 plays most mp4 files natively. Make sure you assign it in Serviio to the PS3 profile. If the files still don't work, they must have something unique about them - we need to find what that is first. Can you post details of the files that are not working - see
here for details - in this case Media Info will yield better info.
Ps. How many are we dealing with?